Now that we have passed in review the whole of the Anthropoid species inhabiting the New World, a short account of the regions to which they are confined will be of some interest. The most northern limit of Monkeys is, as mentioned above, the State of San-Louis Potosi, about the latitude of 23° North. Their most southern limit attains to nearly 25° of South latitude. They are now confined to the Mexican and Brazilian sub-regions of what has been defined as the Neotropical Region, by Dr. A. R. Wallace, in his great work, "The Geographical Distribution of Animals." The Mexican sub-region belongs to the Neotropical Region, one of those six great areas into which the globe has been divided off by Dr. Sclater on the basis of the geographical distribution of the animals that now inhabit it--the final product of the slowly-changing features of the earth's surface, and of the form, structure, and habits of its animal and vegetable life. The Mexican sub-region forms the northern part of the {247}Region, and, to condense Mr. Wallace's account of it, it is of comparatively small extent; but the whole of its area is mountainous, being, in fact, a continuation of the great range of the Rocky Mountains. It varies in elevation above the sea from 6,000 to 18,000 feet. "With the exception of the elevated plateaus of Mexico and Guatemala, and the extremity of the peninsula of Yucatan, the whole of Central America is clothed with forests; and as its surface is much broken up into hill and valley, and the volcanic soil of a large portion of it is very fertile, it is altogether well adapted to support a varied fauna, as it does a most luxuriant vegetation." In this region only species of Spider-Monkeys (_Ateles_), of Howlers (_Alouatta_), of Capuchins (_Cebus_), of Night-Monkeys (_Nyctipithecus_), and of Squirrel-Monkeys (_Chrysothrix_) are found. The Spider-Monkeys and the Howlers alone extend so far North as Mexico, and the Night-Monkeys reach to Nicaragua, while the Squirrel-Monkeys and Capuchins have penetrated no further than to Costa Rica.